In this 2011 photo, crews place concrete on the Atlantic side of the new locks.

What's it all about?

PANAMA CITY (AP) — A look at the Panama Canal and its newly expanded locks, which are set for a test run this week and a formal launch June 26.

THE CANAL

Inaugurated on Aug. 15, 1914, the Panama Canal was constructed by the United States between 1904 and 1913 at a cost of $375 million, building on an earlier, French-led effort that fizzled out. An estimated 20,000 workers died during French control of the project, many due to tropical diseases such as malaria, and 5,600 more perished during U.S. construction. The canal revolutionized global sea traffic by short-cutting long voyages around Cape Horn at the tip of South of America.

OPERATIONS

The canal was under U.S. control until a 1977 agreement between Presidents Jimmy Carter and Omar Torrijos paved the way for its transfer to Panama on Dec. 31, 1999.

Canal authorities say it has generated $10 billion in direct income for the Panamanian state between 1999 and 2015. Along with related economic activity, the canal is responsible for about 40 percent of the country's GDP. An average of 35 to 40 vessels transit the waterway each day, and the canal is estimated to handle some 6 percent of world maritime commerce.

THE NEW LOCKS

The $5.25 billion project was initially scheduled for completion in October 2014, roughly coinciding with the canal's 100-year anniversary. However it has been delayed due to factors including slow approvals for concrete to use in the locks, labor strikes and some leaks that were detected late last year.

The expansion includes two new sets of lock complexes, one on the Pacific coast on the outskirts of Panama City and one on the northern coast at the city of Colon. The locks are 180 feet wide and 1,400 feet long, big enough to accommodate so-called New Panamax-class vessels that are seen as the future of global shipping. Ships up to 160 feet wide with a draft of about 50 feet can now fit in the locks.

New Panamaxes are 1,200 feet long — more than three football fields, and nearly equivalent to the height of the Empire State Building. They are capable of carrying 13,000 to 14,000 cargo containers, about 2.5 to 3 times as many as those that currently can use the locks.

In a recent report, the International Monetary Fund estimated that the canal expansion will reduce global maritime shipping costs by $8 billion a year.

ON LAKE MIRAFLORES, Panama — Waiting to guide a cargo carrier toward the Panama Canal's southern locks, Benjamin Russo gazed from his tugboat at another vessel headed north toward the Caribbean Sea.

At 650 feet long and loaded with automobiles, it was a massive ship. Yet it pales in comparison to the so-called New Panamax behemoths, up to 1,200 feet in length, which within days will begin transiting the waterway. A dress rehearsal is planned today or Friday when the first of the larger vessels will cross through the newly expanded locks.

Few public works projects have captured the world's imagination like the Panama Canal, which opened in 1914 and revolutionized the shipping industry by connecting the Atlantic and Pacific, short-cutting sea voyages around the tip of South America. Since passing from U.S. to Panamanian control in 1999, the canal and related economic activity have come to contribute nearly 40 percent of the Central American nation's GDP.

Already a year and a half behind schedule and eagerly anticipated, the $5.25 billion expansion is expected to double the canal's capacity, tap new markets such as liquid natural gas shipments and cut global maritime costs by an estimated $8 billion a year. Around the Western Hemisphere, ports have been making their own overhauls to receive the vessels, which are more than three football fields long, can carry about 2.5 times as many containers as those currently using the canal and are seen as the future of world shipping.

But as Panama readies for its launch party on June 26, Russo and the other 150 or so tugboat operators who work the waterway are nervous. Under the new system, they'll have to engage in tricky maneuvers in a confined space inside the locks themselves, trying to keep the bulky New Panamaxes from banging into the walls or even crushing the tugs if they lose control.

“Imagine when we're in front of the prow of those other monsters and have to tie ourselves to them,” Russo said. “If something goes wrong with the tugboat and that ship keeps moving, I may not have time to get out of the way.”

Under the old system, tugboats' engagement with ships has been limited to guiding them in open waterways and to the entrance of the locks, where powerful locomotives known as “mules” take over, latching on and keeping the vessels in place as the water level is raised or lowered.

There are no mules in the new setup. Instead tugs will approach a ship, latch on at both the bow and stern and accompany it inside the 1,400-foot locks. With the lock doors closed on a 1,200-foot New Panamax, there's little room to operate for the roughly 90-foot tugs positioned both fore and aft.

The shipping vessels will be running on their own propulsion throughout, and be under the control of a canal pilot who goes on board to steer. Communication between the tugs and the pilot will be key.

Experts say it's similar to locks already functioning elsewhere in the world, such as parts of the United States and Antwerp, Belgium, and that it works just fine. But with increased human involvement comes increased possibility for human error, and there will be a steep learning curve for tug operators and pilots.

“I believe there is some risk increase that's going to require a lot more training and getting used to,” said Richard D. Hepburn, a retired U.S. Navy captain and author of “History of American Naval Dry Docks.”

A mechanical failure such as a broken mooring or a winch or engine outage could complicate things. Panama is prone to violent storms, and analysts said there will likely be some sort of protocol for adverse weather.

“If there's a 70 mph crosswind blowing, well, you may not want to try maneuvering in until the wind abates,” said Jack Leary, a marine engineer and naval architect at Leary Engineering in New Orleans.

Canal authorities say they are well equipped to deal with extreme conditions. Officials say over 60 of the 289 canal pilots and more than a third of the 150 tugboat captains have undergone simulator training. The canal became fully operational May 31 after running more than 1,000 virtual trials involving 300 possible scenarios.

Canal administrator Jorge Luis Quijano said the skills the pilots and tug operators need are being provided through a four-stage training process. Operations will ramp up slowly, with just four boats a day transiting the new locks through the end of September to allow captains to gradually gain experience.

“Bit by bit, we want to go about removing that anxiety,” Quijano said.

Nevertheless, captains worry their training has not been enough as Day One of operations looms a little over two weeks after the trial.

“They can run a million simulations,” said Paul Bingham, a shipping economist at EDR Group, but “you have to actually put the humans in control with all the other variables of the real world conditions of weather and lighting.”

Tugboat captains are also concerned about the moment when they will approach the large ships and attach lines while still in motion. If not done properly, they say, the hydrodynamic force created by a New Panamax could sink their own boats.

“Obviously we have that fear,” said Cristobal Falquez, who has been a tug captain since 1999.

Moreover, they'll have to guide the ships through 50 miles of interior waterways and often-foggy curves, including a narrow stretch nicknamed “the snake.”

The captains' concerns about risks are leading to demands for better pay.

“The work has to be done,” Russo said. “The thing is you have to mitigate the risks, (and) you have to remunerate for running that risk.”